A student observed a Paramecium under the low power objective of a microscope (100x) and then under high power (400x). The image of the Paramecium under low power, compared to the image of the same Paramecium under high power, would be

A) Smaller and in a darker field of view

B) Smaller and in a brighter field of view

C) Larger and in a darker field of view

D) Larger and in a brighter field of view

Correct Answer: Option B - Smaller and in a brighter field of view

As you increase magnification from low to high power, the image gets larger and because the lens is bigger, less light is allowed in under high power. Therefore, under low power the image is smaller but brighter.

Hence, the options A, C and D are incorrect.

Which instrument is most commonly used to observe the external features of a grasshopper's abdomen?

A) Dissecting microscope

B) Ultracentrifuge

C) Microdissection instrument

D) Electron microscope

Correct Answer: Option A - Dissecting microscope

The dissecting microscope allows you to view CD images up to 50x magnification. It is commonly used in dissections.

Incorrect Answers:

The ultracentrifuge spins liquids and separates the contents by their density.

Microdissection instruments are used to manipulate microscopic organelles (such as transferring nuclei).

Electron microscopes can magnify an image up to 2,50,000x and are used to see microscopic details.

Hence, options B, C and D are incorrect.

To study the structure of phloem and xylem tissue, sections can be prepared and observed under a:

A) Centrifuge

B) Triple beam balance

C) Incubator

D) Microscope

Correct Answer: Option D – Microscope

To observe the small structures such as cells, tissues, etc., it would be necessary to observe them with an increase in magnification.

Incorrect Answers:

A centrifuge is equipment, driven by a motor that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis. The centrifuge works using the sedimentation principle, where the centripetal acceleration is used to evenly distribute substances of greater and lesser density. It can be used for viable counts, when shaking the culture e.g. yeasts, out of suspension.

A triple beam balance is a type of balance commonly used in the laboratory to determine the mass of items. Sliding weights called riders on three beams are used.

Incubator is a laboratory instrument used to maintain a bacterial culture at a particular temperature for a set length of time.

Hence, options A, B and C are incorrect.

A sample of food containing one type of a large molecule was treated with a specific digestive enzyme. Nutrient tests performed on the resulting products showed the presence of simple sugars, only. Based on these test results, the original large molecules contained in the sample were molecules of:

A) Protein

B) Starch

C) Glucose

D) DNA

Correct Answer: Option B – Starch

Starch is a complex sugar found in food items consumed. When starch is broken down simple sugars are formed.

Incorrect Answers:

Proteins and DNA cannot be broken down into simple sugar.

Glucose is a simple sugar by itself which can be easily absorbed by the digestive system.

Hence, options A, C and D are incorrect.

Diagrams, tables, and graphs are used by scientists mainly to

A) Design a research plan for an experiment

B) Test a hypothesis

C) Predict the independent variable

D) Organize data

Correct Answer: Option D – Organize data

Diagram, tables and graphs help to organize the data and transfer numerical values into a form which can be compared and analyzed, thus testifying the hypothesis.

Incorrect Answers:

Designing a research plan includes more than diagrams, tables, and graphs.

A hypothesis can be tested only by conducting the actual research.

Predicting the independent variable is a part of the research plan and is not related to diagrams, tables or graphs which help to organize the data gathered from the experiment.

Hence, options A, B and C are incorrect.

Which statement describes the best procedure to determine if a vaccine for a disease in a certain bird species is effective?

A) Vaccinate 100 birds and expose all 100 to the disease.

B) Vaccinate 100 birds and expose only 50 of them to the disease.

C) Vaccinate 50 birds, do not vaccinate 50 other birds, and expose all 100 to the disease.

D) Vaccinate 50 birds, do not vaccinate 50 other birds, and expose only the vaccinated birds to the disease.

Correct Answer: Option C - Vaccinate 50 birds, do not vaccinate 50 other birds, and expose all 100 to the disease.

Options A, B and D do not provide scope for testing the exposure to disease of non vaccinated birds, which is very important to determine the effectiveness of the vaccine.  Hence, they are incorrect.

A cover slip should be used for preparing a

A) Frog for dissection

B) Wet mount of elodea (a simple plant)

C) Test to determine the pH of a solution

D) Solution of iodine for food testing

Correct Answer: Option B - Wet mount of elodea (a simple plant)

A cover slip is used to prepare wet mount of minute objects such as a leaf section of elodea which is a simple aquatic plant, so that it can be studied under a microscope.

The other C options do not have elements which need to be observed under a microscope. Hence, they are incorrect.

When a plant cell in normal water is moved into a A0% salt solution, the cytoplasm and vacuole of the plant cell shrink. The reason for this change is:

A) More salt moving out of the cell than into the cell

B) More salt moving into the cell than out of the cell

C) More water moving into the cell than out of the cell

D) More water moving out of the cell than into the cell

Correct Answer: Option D - More water moving out of the cell than into the cell

The reason for movement of more water out of the cell than into it is the process of osmosis. Osmosis is the diffusion of water through a semi-permeable membrane, from a low concentrate solution (high water potential) to a highly concentrated solution (low water potential), up a solute concentration gradient. Hence, causing the cytoplasm and vacuole of the plant cell to shrink.

Hence, options A, B and C are incorrect.

The width of a human hair is 0.A millimeter. The width of this human hair in microns is

A) 1 u

B) 10 u

C) 100 u

D) 1000 u

Correct Answer: Option C – 100 u

One millimeter (mm) is equal to 1000 microns or micrometers (um).

Hence 0.1 mm = 100 u

Hence, the options A, B and D are incorrect.

A student formulated a hypothesis that cotton will grow larger bolls (pods) if magnesium is added to the soil. The student has two experimental fields of cotton, one with magnesium and one without. Which data should be collected to support this hypothesis?

A) Height of the cotton plants in both fields

B) Length of the growing season in both fields

C) Color of the cotton bolls in both fields

D) Diameter of the cotton bolls in both fields

Correct Answer: Option D - Diameter of the cotton bolls in both fields

The data directly providing information to test the hypothesis is the diameter of the cotton bolls. Hence, it is the information to be collected to support the hypothesis.

Height of the cotton plants, length of the growing season and color of the cotton bolls are irrelevant to the hypothesis. Hence, options A, B and C are incorrect.